Means for making elbows



Aug, 16, 1955 P. D. WURZBURGER MEANS FOR MAKING ELBOWS Original FiledAug. 20, 1945 4 Sheets-Sheet l PAUL D. WUEZBl/RGEB.

Aug. 16, 1955 P. o. WURZBURGER 2,715,432

MEANS FOR MAKING ELBOWS Original Filed Aug. 20, 1945 4 Sheets-Sheet 2 /27 E? 8 INVENTOR.

16, 1955 P. D. WURZBURGER 2,715,432

MEANS FOR MAKING ELBOWS Original Filed Aug. 20, 1945 4 Sheets-Sheet 3 D//-Z 0 5l 32 3a 3/ 30 3o @32 Fgja. [fig/4. 117g. /5. 1%2/6.

IN VEN TOR.

16 P001. 0 WUEZBUPGE/Q.

W EMS ///arrre 5 1955 P. D. WURZBURGER 2,715,432

MEANS FOR MAKING ELBOWS Original Filed Aug. 20, 1945 4 SheetsSheet 4 1I'Il IN VEN TOR.

Unite States Patent 0 MEANS FOR MAKING ELBOWS Paul D. Wurzburger,Cleveland Heights, Ohio, assignor to Northern lndiana Brass Company,Elkhart, Ind., a corporation of lndiana Continuation of abandonedapplication Serial No. 611,600, August 20, 1945. This application April12, 1951, Serial No. 220,632

1 Claim. Cl. 15348) This invention relates to a metal working and to amethod of making tubular elbows and elbow fittings and more particularlyto a method of making short radius wrought elbows.

This application is a continuation of my copending application SerialNo. 611,600, filed August 20, 1945, now abandoned.

In the art to which my invention pertains it has been known to makeelbows of relatively large radius by merely forcing a tubular blankwithout internal support through the curved channel of a forming die.Such methods are limited in their use and application at the point wherewrinkling and undesirable deformation of the metal begins to occur asthe radius of curvature, in relation to, inter alia, the diameter of thedesired elbow, is decreased. Having in mind the variations resultingfrom the use of different metals and the different relations of wallthickness to tube diameter, it may be taken as a general propositionthat undesirable wrinkling limits this prior art method to makingwrought 90 elbows or bends having a minimum radius of curvature, asmeasured on the external surface at the inner bend, about equal to theoutside diameter of the tube.

When in the prior art it has been desired to make elbows of shorter orsmaller radii in relation to diameter the teaching of the prior art hasbeen to give the tube ternal support for the extruded leg or posteriorportion of the blank through supporting mandrels whereby to resist thetendency of the material to collapse inwardly upon being forced to takethe small radius turn.

In the methods where internal support has been provided to resist thetendency of the walls of the blank or elbow to collapse inwardly or towrinkle, there have been concomitant limitations, namely that resistanceto the fornation of wrinkles has built up, oft-times greatly orexcessively, an increased resistance to forcing the work around thecorner or bend of the forming channel. The effect of the internalsupport which requires the greater force to move the blank through thedie is not limited merely to requiring greater working efforts to bringabout the formation of the elbow but along with the greater workingeffort follows the greater stress and working of the metal of the blankas well as a tendency to thicken certain wall portions and/or thin outother portions and to expand the walls whereby to increase thefrictional load between the outer surface of the blank and the channelof the die. These difficulties increase as the ratio of the radius ofcurvature to the diameter of the elbow is reduced so that the methodswhich rest upon internal sup- D. On

port for the blank during the forming of the bend run toimpracticabilities in waste of time, power or material, or inunsatisfactory products, excessive wear or injury to the dies, mandrels,tools and machines used to do the work. Moreover these inherentlimitations in the methods which are based upon internal support for thematerial of the elbow of necessity bring about reductions in the speedof production and increases in cost as well as many practicaldifficulties inherent in the very nature of the internal supportingmeans or mechanisms such as balls, articulated mandrels or in otherinstrumentalities.

It is among the objects of my invention to provide an improved method offorming elbow fittings which seeks to avoid the various diificultiesdiscussed above by a simple process which is economical from theproduction point of view, yet practicable and satisfactory in operation.A more specific object of my invention is to provide a method of formingshort radius elbow fittings of high and uniform strength, utility andquality. By short radius I have in mind that the ratio of the radius ofthe external surface of the inside corner of the elbow to the outsidediameter thereof be less than unity, and preferably a small fraction ofunity such as about one third to one quarter.

Another object of my invention is to produce a method of making shortradius elbows in which the walls of the blank and elbow aresubstantially relieved of deleterious stresses and strains during theformation of the bend thereof and more particularly during the formationof the bend in the elbow during the step of forcing the blank through anelbowed channel of a forming die.

Another object of my invention is to preserve a substantially uniformwall thickness in and throughout the parts of the elbow formed accordingto my invention. Another object of my invention is to provide a methodof forming elbows which can be carried. out with the expenditure oflittle or a minimum of power for forcing the blank through the die and/or working the material from an initial straight tubular form to afinished short radius elbow form. Another object of my invention is tosubstantially eliminate spring back in the elbow after the same isremoved from the forming die or mechanism.

A primary object of my invention is to provide a method of formingcommercially useful right angled elbows or elbow fittings having such asmall ratio of radius of curvature to diameter that upon their beingsubjected to bending as by being forced through a forming die withoutinternal support that the wall of the metal, particularly that adjacentto and beyond the inside corner thereof, tends to wrinkle and have otherdeformations from its ultimately desired shape. Another and morespecific object of my invention is to provide a method for forming shortradius elbows in which resistance to the formation of the bend of theelbow as by forcing a tubular blank through a ring angled channel of aforming die is maintained at a low value by the complete, substantial orpartial elimination of internal support for the walls of the material ator adjacent the bend of the elbow while the same is being formed.

Other objects and advantages of my invention will appear from thefollowing description of preferred and modified forms thereof referencebeing; had to the accompanying drawings in which Figure 1 shows inlongitudinal cross section a tubular blank positioned in an initialposition in one of a pair of split forming dies through which the blankis to be forced to give it its elbowed form; Figure 2 is a view similarto Figure 1 showing the blank in cross section in an advanced positionin its movement in the channel of the forming dies; Figure 3 is a viewsimilar to Figure 1 showing the blank in fully advanced position atsubstautially the end of the forming stroke; Figure 4 is a top plan viewof the partially formed elbow in thecondition shown in Figure 3; Figure5 is an end elevationof the same partially formed elbow shown in Figures4 and 3; Figure 6 is a view taken partially in the plane of the split ofthe forming dies showing the partially *finished elbow in the positionof Figure 3 preliminary to the entrance of an ironing mandrel; Figure 7is a view similar to Figure '6 in respect to the forming dies and thepaits'contained therein and associated therewith showing the "ironingmandrel in advanced position; Figure 8 is a viewsimilar to Figure 7showing an ironing mandrel "in a retracted position following the stepdepicted in Figure 7; Figure 9 is a view of a modified procedure andapparatus, the view being similar to that "of Figure '1 and comprising asection taking in the plane of the split of the forming dies with theblank in 'its initial preformed "position and 'with a modified form ofironing 'ma'ndrelin place; Figure '10 is a view similar to Figure 9'showin'gthe blank 'in'the position advanced from that shown in Figure'9; Figure 11 is a view similar to Figure 10 showing the blank in itsmost advanced position preliminary tomovement or withdrawal of theironing mandrel; Figure 12 is a *view similar to Figure 11 showing theironing mandrel in 'its withdrawn position after the same has ironedout'the wrinkles from the extruded leg o'fthe 'elbow; Figures 13, 1'4,1'5 and 16 are respectively transverse sectional'vie'ws of theironingmandrel shown in Figures 9 to 12 inclusive taken along the lines1313,14--14, 15-15, and 1616 of the ironing mandrel of Figure 12; Figure '17is a'modified form of blank in the form of a deeply drawn cup or tubewith a closed end; Figure 18 is a section through the blank of Figure17, the latter being disposed in the channel of a forming die similar tothe forming die shown in the above figures; Figure 19 is a view similarto Figure 18 showing the blank of the form of Figure 17 in its ad vancedposition having been forced around the bend of the forming die; andFigure 20 is a view similar to Figures '18 and 19 showing the blank incross section in its finished form within the channel of the formingdie.

'To accomplish the objects and advantages of my inventionl place atubular blank of malleable and ductile material to be formed into theelbow in the channel of a forming die which has a short radius elbowedform su'bstant'ially corresponding to the external form of the -finishedelbow. Then preferably without substantially supporting the blank-interiorly 1 cause 'to 'be exerted a longitudinal force on the trailingend of blank remote from the bend of the elbow and thereby forciblyadvance the blank through the bend of the channel of the die to give theelbow its angled form while permitting the material of the leading endof the blank to become wrinkled and deformed, but not excessively so,asit passes through and beyond the bend of the forming channel. I'hav'efound that at the completion of this step of the forming operation thatthe trailing leg and thebend of the partially formed elbow, see Figures3, 4 and '5, are not only not deleteriously deformed but are in factsubstantially superior in conformation, size, internal stress, Wallthickness, contour and the like to similar parts formed by prior artmethods in which effort has been made to provide internal support forthose parts of the blank which tend to collapse or wrinkle whiletheblank is being forced through the angled channel of the die."Substantially all the wrinkling and deformation of the whole blank isconcentrated in the leading, i. e., extruded leg of the piece, but sincethisleg has been free from internal support and has been permitted totake its own shape it 'has' not been unduly stressed nor has it causedundue stresses, thickening or thinning out of other parts of the piece.After the piece has been given its initial elbow form, albeit withan'imperfect'leading leg, I thereafter,'by means presently to bedescribed, remove the imperfections from theleading legand'have for myproduct a short radius elbow with the desirable characteristics soughtandrnen "tioned above.

' bend 2 of'the channel ofithe die.

I have found my method to be practicable and advantageous when practicedwith such malleable and ductile metals as hard or soft copper, lowcarbon steel, stainless steel and aluminum alloys as are commonlyemployed in commercial tubular stock. Without trying to state all thediiferent kinds of metals or the range of sizes or relations of wallthickness to diameter in different materials with which my method may beadvantageously practiced, my observations have been that while tubes orblanks or excessively soft metals and/ or large diameters and/or thinwalls require less eifort to bend, the apparent advantage may tend to bemore than offset when some or all of these characteristics admit ofexcessive thickening, wrinkling or other undesirable effects in the workpiece. The converse follows With excessively hard materials, smalldiameters and/or thick walls. Having these limitations in mind I haveprovided, as will more fully appear below, precautionary steps forcontrolling wrinkling, for example, in the leading leg of the elbowwhereby to extend the useful range of my invention against the apparentlimitations mentioned above. The following descriptions andillustrations of preferred and modified forms of my invention are basedespecially on tests and demonstrations employing one-half inch :0. 'D.copper tube, soft temper, with 0.035" wall thickness; the finishedelbow'turning at about .a one-eighth inch inside radius of curvature.

A preferred form ofcarrying out the method according to my invention isillustrated in Figures 1 to 8 inclusive. in all these figures except 4and .5, 'Ive illustrated diagrammatically the half die D of a split pairof forming dies, the parting plane of which is in the plane of thedrawings. Such die halves are opened in the iknownway to receive theblank, or piece, closed to form the forming channel of circularcross-section (-the half channel C being shown in the 'half die D), heldclosed=during the forming operation and finally opened to permit:removal of the piece after it has been formed. The channel C has astraightcylindricalenteringsection l long-enough to receive the tubularblank or work piece B, a bend 2 With inside radius r and diameter d, thelatter beingiequal to the diameter of the entering section '1, and thestraight cylindrical forming section 2, the latter having its axis asshown at 90 to the axis'of the entering section 1. As shown in Figure lthe blank B is preferably of'the right cylindrical form withsubstantially square-ends and preferably hasan-externaldiametersubstantially equal 'to the internal'diameter d-of 'the-channel-C. Apower driven ram R enters the upper (as viewed) end of the section l ofthe'channel C with its shoulder 'S engaging the end of the piece =8 andits pilot P-entering and closely fitting the trailing end of the piece.In Figure l the ram R is in position preliminary to exerting the force,downwardly as viewed inFigure 1, whereby to urge the blankaround the Thepilot P m'ay-be as long as the trailing leg ofthe finishedelbow.

With the blank 3 positioned in the die D as shown in Figure 1, andwithout internal support "fOl Ol' engagement-of the blankother thanbythe ram R and the=interior surface after channelC, downwardmovement-of the ram forces theleading end'ofthc blankinto the bend 2ofthe-channel C asshownin the mid-stof its travel in Figure '2. Here itwill be-observed that the inner'leading edge 10 of the blank tends tocontinue -in-a straight line ratherthan to-turn the corner whereas theouter leading edge 11 of the blank is being forced around the-curvedouter Wall'of the-channelC and has substantiallyswung throughan arc ofabout 90. As 'will'also beobser'ved in Figure 2 the wall o'f the blankadjacentthe-outer-curve of the bend -2 has spaced itself a little awaytherefrom whilst the'open =leading end 1 2 of 'the blank has taken anirregular form incident to the permissivedeformation that takes placeduring the travel of the *work from the position shown in Fig. l 'tothatof Fig. 3. The view of Figure 2 is intended 'to'illustrate the positionof'theparts at the instant of their continuous movement through thisstage of the advance of the blank through the channel of the formingdie. Further continued movement of the ram from the positions shown inFigures 1 and 2 brings the parts to the position shown in Figure 3 andthus to the end of its first forming step. At the end of the stroke ofthe ram R, as shown in Figure 3, it will be observed that the elbowedpiece has been given its general configuration with the leading inneredge as well as the outer wall of the bend of the blank returned tocontact with the wall of the channel C and the outer leading edge 11 ofthe blank has come out of contact with the adjacent wall of the channel.The open leading end 12 has taken a somewhat different form from thatshown in Figure 2, and the upper surface of the extruded leg containsdeep though smoothly formed wrinkles 13 and 14, see also Figs. 4 and 5wherein the elbowed piece B is shown in full as it would appear ifremoved from the dies after having been worked to the state of Figure 3.In this stage of the formation of the elbow it will be observed thatwhile the inner wall of the elbow has tended to thicken a little at thecorner that the outer wall 16, particularly at the bend, has not beenweakened or materially reduced in thickness.

tial interference with the natural bending and working of the metal haspermitted the various parts of the piece to flow longitudinally andcircumferentially relative to Moreover it has been my observation thatfreedom from internal support and substan each other with relativefreedom whereby to accommodate themselves to the change in form of thepiece without requiring excessive (wall thickening) pressure from theram and without fracture of or creating deleterious internal stresseswithin the piece.

Preferably the work piece 13 is not removed from the dies after theabove step as shown in Figure 3, is completed but rather the working ofthe piece is continued as shown in Figures 6 and 7. In Figure 6 the workpiece and the ram R are shown in the same condition as in Figure 3. InFigure 6, however, there is shown in the left of the figure a second ramor ironing mandrel M connected with and actuated by such means as anhydraulic cylinder H whereby to give the mandrel M a rightward andleftward movement, as viewed in Figures 6, 7 and 8, under appropriatecontrols, not shown, to

carry out the second step of my method about to be de- 7''.

scribed. The mandrel M has a rounded nose 2t) and enters the section 3of the channel C of the dies D and the open leading end 12 of the workpiece to expand the same as well as expand and iron out the wrinkles 13and 14, to form the intended finished internal and external diameters ofthe extruded leg of the piece. Preferably the mandrel M enters thechannel C through a guiding sleeve 21 which has substantially thefinished wall thicl ness of the work piece so that the mandrel is guidedin axial alignment with the finished wall thickness desired to be formedin the leading leg of the work piece. Forcible movement of the ironingmandrel M from left to right as viewed in the drawings advances themandrel from the position shown in Figure 6 to the position shown inFigure 7 whereby it will be seen that the wall of the leading leg of theelbowed piece has been brought back to substantially cylindrical form,eliminating the wrinkles l3 and M and opening the open leading end 12 ofthe elbow to substantially true right cylindrical configuration. Whilethe ironing mandrel M is forcibly advanced from the position shown inFigure 6 to the position shown in Figure 7 the ram R is held in its mostadvanced position as shown in Figures 3-7 whereby to resist the tendencyof the piece to be moved backward in the channel by the entering strokeof the mandrel M. During the inward and ironing stroke of the mandrel Mnot only is the wall of the leading leg of the piece expanded radiallyand brought to a more uniform wall thickness but also is the thicknessand fullness of the outer bend 16 of the elbowed piece enhanced wherebyto eliminate the 1 and tendency of the elbow to spring or spring-back toa somewhat different form than the angled form of the channel of thedie.

After the mandrel M has been advanced to substantially its point ofmaximum penetration as shown in Fig. 7, it is then forcibly withdrawnfrom the leading leg of the elbow, see Fig. 8, its movement during itswithdrawal adding to the burnish of the interior of the leg of the elbowand perfecting the desired form and finish thereof. Preferably the ram Ris withdrawn from engagement with the trailing end of the elbow afterthe ironing mandrel M has passed from contact with the leading legthereof, see Fig. 8. My method may be advantageously practiced either bydirect manual control of the movements of the ram and mandrel or byappropriately correlated automatic or semi-automatic mechanisms andcontrols which can be adjusted to the practice and precepts of myinvention.

When the parts have assumed the position shown in Fig. 8 it remainsmerely to open the dies D and remove the elbowed piece. Thereafter byappropriate steps known and practiced in the art before my invention,the respective ends of the elbowed piece may be treated by way ofenlargement or other trimming or sizing to form appropriate sockets toreceive tubes in capillary or other bonded joints or otherwise treatedappropriately for the purposes to which the elbows are intended to beused.

The obliqueness of the leading end. of the elbows as shown at 12' inFigure 8 is a thing which I have found to be substantially insignificantin respect to the essential steps of my process and the final finishingor sizing of the product, particularly with the materials which I haveemployed as mentioned above and in the so-called smaller sizes ofelbows, i. e., about I or less outside diameter. In the event that theobliqueness of the leading end of the elbowed piece in the semi-finishedform shown in Figure 8 takes on a deleterious significance in point ofthe final sizing, finishing or truing operations to be performed afterthe novel steps of my instant method are performed, then I find that Ican substantially control the obliqueness of the opening 22' by cuttingthe end of the blank a little on the bias rather than truly in the rightcylindrical form as shown in Figure 1. Where the blanks are cut on thebias I place them in the die so that the longer wall will be the outsidewall of the bend of the elbow with the result that in the piece as shownin Figure 8 the outer leading edge 11 will lie more nearly directlyopposite the outer leading edge 10. Otherwise I prefer to use blankswith right angled ends since no care need be taken with re spect to theposition of the blank around its own axis in the dies.

Referring to Figures 9 through 16 a modified form of my method will nowbe described. Here, as shown in Figures 9 to 12 inclusive, I prefer toemploy the same dies D, having the same forming channel C which in turnhas the same entering section 1, bend 2 and forming section 3 allsubstantially identical in the structure and function as first abovedescribed. Here also I may employ the same ram R with the shoulder S andpilot P, the action and function of which may be the same orsubstantially as above described. As shown in Figure 9 the blank tubularwork piece B may be the same as the piece B shown and described inFigure 1 and may fit the channel C of the die and be advanced therein bythe ram R into and through the bend of the channel by the same movementof the ram R as above described.

In this modified form of my invention, however, I employ a differentform of ironing mandrel N, see also Figures 13 to 16, and operate themandrel N in a specifically different way from that in which the mandrel M is operated. As shown in Figure 9 the mandrel N has the whole ofits working end 30 lying within the forming section 3 of the channel Cwith its head part 31 lying within the bend 2 of the channel. I preferthat the cylindrical shank portion '32 of the mandrel N slide with asnug sliding fit within a guide sleeve or tube 33 which preferably hassubstantially the same wall thickness as the ultimately desired wallthickness of the leading leg of the elbow whereby to guide the mandrel Naxially in its movement within the channel and to support the lower sideof the mandrel especially during the latter part of its ironing strokeas will be more fully described below. The mandrel N like the ram R andmandrel M is actuated by appropriate actuating means such as a hydrauliccylinder or otherwise whereby to give forceful rightward and leftwardmovement as viewed in the drawings in alignment with the axis of theforming section 3 of the channel C. The pilot sleeve 33 may also beappropriately actuated by power means not shown, whereby the end of thesleeve 33 may be disposed as much :or little within the section 3 of thechannel as may be desired in relation to the leading end or open end ofthe extruded leg of the elbow.

As shown with particular reference to Figures 13 to 16 the working end3tl'of the mandrel N departs from the cyiindrical form of the shank 32thereof by a tapering relief cut away from the upper side of the mandrelas viewed in these figures, whilst the lower part of the working end ofthe mandrel retains a substantially semi- :cylindrical cross sectionfrom the end of the shank portion 32 up to the head portion 31 thereof.As shown more particularly in Figure 15 the top surface of the head 31is substantially semi-cylindrical lying in a pro jection of the topsurface of the shank .32. This semicylindrical surface extendsapproximately between the points 34 and 35 rightwardly and leftwardly,as viewed in Figure 9, and merges leftwardly, into a rounded uppersurface which merges smoothly with the upper relief of the working part30 of the mandrel at and about the point and corner 36. The forward anddownward face of the head 31, comprising the surface opposite the outerbend Z of the channel, is similar to the adjacent surface of the bendand thus substantially spherically formed whereby to be spaced from theouter bend of the channel approximately the thickness 'of the wall ofthe blank. As shown in Figure 9 it will appear conversely that the point36 at the place of maximum relief is most widely spaced from the innercorner of the bend 2 of the channel whereby to permit the inner leadingedge 10 of the blank B to pass with desired freedom beyond the innerturn of the channel without substantially contacting or withoutexcessive forceful bearingupon the mandrel N as the blank is advancedthrough the forming die, see Figure 10.

In this form of my invention while I do not entirely avoid all interiorsupport or contact for the blank as it is advanced in the forming die,'I have found thata mandrel shaped substantially like the mandrel N withthe greater relief on its upper face, i. e., its face adjacent to andfacing the inner turn of the channel, exerts little enough force orfriction upon the inner surfaces .of the blank as the latter is forcedthrough the channel as to preserve substantially the advantages of thecomplete absence of internal support for the blank during the bendingoperation. Thus when the ram R begins its stroke, downwardly as viewedin the drawing, forcing the blank along the section 1 of the channel andinto and through the bend 2 thereof and in part into the section 3 ofthe channel, the leading end of the blank encompasses and in the mainslides freely past the head of the mandrel N as well as substantiallyall of the working end 30 thereof with much the same facility ofmovementthat the blank has in the first step described with reference to Figures2 and 3 above. As shown in Figure vl0, the outer leading edge 11 of theblank passes between the smooth outer and lower surface of the head 31of the mandrel whilst the .inner leading-edge 10 of the blank is bentaway to the left as viewed in Figure 10, under the influence of themovement of the 'body of the blank and the curvilinear movement of theouter leading edge 11 and adjacent parts. Continued movement of theblank B beyond the position shown in Figure 10 and approaching theposition shown in Figure 11 may induce the inner leading edge 10 of theblank to contact more or less the upper relieved face of the working endof the mandrel more or less forcibly but with much less than harmfulresistance to the movement of the blank through the forming channel. Atthe end of the forming stroke of the ram R the blank B will have beengiven its elbowed form and the leading leg of the blank will havesubstantially encompassed the working end 30 and the mandrel Nas shownin Figure 11. The inner wall of the leading leg of the elbow will bewrinkled as at 13' and 14 substantially corresponding to the wrinklesBand 14 above described, and the open leading end 12" of the piece will,have a configuration more nearly corresponding to the end .12 as shownin Figure v8, than the .end 12 as shown in Figures 3, 4 and 5 above. Itwill also be noted in this form ofmy method that the outer wall of thebend'of the .elbow has been maintained in substantial contact throughoutthe whole of this forming step with the lower and outer working face ofthe head .of the mandrel.

The elbowed blank, however, as shown in Figure 11 has been given itselbowed form with great freedom of the parts of the leading .leg towrinkle and take paths of longitudinal, curvilinear and circumferentialmovement with respect to the other parts and the axis of the leading legwhereby to be relatively free of deleterious stresses or tendencies tofracture, and similarly the ram R has not been called upon to deliverexcessive forces to advance the blank longitudinally around the bend ofthe channel. Such little resistance as the mandrel N has offered :to themovement of the blank B will have tended in some measure to cause theinner wall 15 to be somewhat thicker than the inner wall 15, Figure 3,of the elbowed blank B and correspondingly the outer wall 16 of theelbowed blank as shown in Figure 11 may well tend to be a little thickerthan the outer wall 16 of the blank -B under the circumstances shown inFigure 3. Following my fundamental teachings, however, it remains inthis modified form, as it did in the preferred form, to iron out orsmooth out the wrinkles and other deformations particularly in theextruded leg of the elbowed blank. Peculiarly advantageous to theinstant form of my method .is the position of the ironing mandrel N, asshown in Figure 11, interiorly of the elbowed blank so that forciblewithdrawal of the mandrel N will by virtue of its form and contour abovedescribed iron out and give the desired cylindrical contour to theleading leg of the elbowed blank. Leftward movement of the mandrel N, asviewed in Figures 11 and 12, will bring the upper semi-cylindricalsurface of the head 31 with its rounded shoulder at 34 intoironingeontact with the wrinkled and deformed inner wall 15 of theleading leg of the elbowed blank ironing the wrinkles out as the head ofthe mandrel progresses leftwardly from the position shown in Figure 11to the position shown-in Figure 12, and placing that portion of the wall15' adjacent the inner turn of the channel in a state of drawing tensiontending to thin the wall more or less especially adjacent the inner bendof the elbow depending upon the tightness of the fit of the head 31 inthe extruded leg ofthe blank B. While the mandrel N is being withdrawnand ironing out the inner wall 15 the mandrel, its working end 30 andthe head 31 are supported in proper axial position by virtue of thebearing of the whole lower semi-cylindrical portion thereof upon theouter semi-cylindrical wall 16' of the leading leg of the elbow and uponthesleeve ,33. When the mandrel N has been moved to the position shownin Figure 12 and after the ram R has been withdrawn as described inconnection with the preceding form .of my method the dies Dmaybe openedand the elbowed blank,

finished in the sense of being properly elbowed, may be removed from thedies for further sizing and finishing treatment in the same way and forthe same purposes mentioned above. Preferably the ram R is not Withdrawnuntil after the ironing mandrel N has been withdrawn to the positionshown for it in Figure 12 whereby to steady the elbow in the channel ofthe die during the ironing operation.

While I have found it practicable to form elbows in this modified formof my method by first causing the ram R to take its whole stroke beforebeginning the ironing stroke of the mandrel N, I have also found itadvantageous to initiate the ironing stroke of the mandrel N prior tothe full completion. of the stroke of the ram R, i. e. the ironingstroke may begin when the ramming stroke is about three-fourthscompleted, i. e., with the trailing and leading ends of the blank atabout the position of the dotted lines 39 as shown in Figure 11.Preferably the ironing mandrel N then moves at a greater speed than theram while both instrumentalities are moving and no substantial wrinklingor undesirable deformation occurs rightwardly of the withdrawing head ofthe mandrel N because the great tendency toward wrinkling andundesirable deformation takes place in the blank more nearly adjacentthe leading end thereof than in those portions of the blank adjacent thebend, see Figures 3, 4 and 11, and cf. Figures 2 and 10. The correlationof the movement of the mandrel N and the ram R may be effected by manualand visual control or by automatic controls known in the art. Where bothmandrels are sought to have motion at the same time, at least within thelatter part of the ramming stroke, an automatic control to initiate themovement of the ironing mandrel at a particular point of the travel ofthe ram will be much preferred if not necessary to bring about thecorrelations of movements last above described. After the parts havefirst arrived at the position shown in Figure 12 the ironing mandrel Nmay be given additional reciprocatory ironing strokes while the ram Rpositions the piece if that be found necessary or desirable.

A further modified form of my method is described with reference toFigures 17 to 20 inclusive. In carrying out this further modification ofmy method I use for a work piece a tubular member or shell T, Figure 17,having a closed end, which preferably is formed by drawing a suitableblank into tubular form. The piece T may have substantially the samerange of wall thickness and diameter as the pieces B and B abovedescribed but since it is conveniently drawn from flat stock theselection of materials may well be modified for this consideration. Toperform the work on the piece T 1 preferably employ the split dies Dwhich may be substantially identical with those above described, thedies containing and forming the forming channel C with its enteringsection 1, bend 2 and forming section 3. To advance the work piece ortubular blank T through the channel of forming dies I employ a ram Qwhich differs from the ram R previously described in that it is made oftwo parts comprising an outer sleeve 4% and an inner punch member tl. Atthe beginning of the forming stroke, as shown in Figure 18, relation ofthe sleeve. to the punch part 41 may be such that the end of the sleeve40 corresponds to the shoulder S of the ram R and the end of the punch41 may correspond to the pilot P of the ram R engaging the trailing endof the blank T in substantially the same way that the ram R engages thetrailing end of the blanks B and B in the preceding descriptions. Boththe sleeve 40 and the punch 41 may be moved together in the initialportion of the forming operation whereby to act in unison, but the powermechanisms, not shown, which move these parts are so constructed thatthe punch 41 may be moved independently of the sleeve 40 under thecircumstances presently to be described. In addition to the ram Q whichhas its movement within and in axial alignment with section 1 of thechannel C, i also provide the ram V which has its movement to and withinthe forming section 3 of the channel C and in axial alignment therewith.The ram V is preferably blunt ended and of substantially the fulldiameter of the channel 3 whereby to present a full abutment to theleading end of the blank T at the times and places to be describedbelow. Appropriate power mechanism, not shown, moves or holds the ram Vfor the purposes presently to appear.

Preferably prior to placing the blank T in the straight cylindricalsection ll of the channel C, the blank is partially filled with afilling material P which may take one of a number of forms consistentwith the precepts of my invention. That is to say, the filler may beliquid such as oil or water on the one hand or on the other hand may bedry granular or plastic material such as common salt (NaCl), sand,polyethylene glycol in the form of the heavier molecular weightssometimes known as carbowax or other granulated, powdered or liquidfillers which while unconfined will otter no substantial internalsupport for the tubular blank as during some or all the time the blankis being forced through the bend of the forming die, but which iscapable of transmitting and exerting high static pressures within theblank when forcibly confined and compressed therein as by movement ofthe punch ll of the ram Q inwardly of the trailing leg of the blank,whereby to compress the filler and to move it forwardly of the blankwhereby to expand the leading leg of the elbow after the latter has beenwrinkled and deformed in the course of its passage through and beyondthe bend of the channel of the forming die. It is also desirable in theselection of the filling material F that the same be easily disposed offrom the interior of the finished elbow after the same has been finallyformed. In using the expression finally formed 1 have in mind the elbowas formed substantially as shown in Fig. 20 of the drawings. Thepreferable quantity of the filling material to be employed or placed inthe blank T prior to the beginning of the work thereupon may vary withinconsiderable limits as will more fully appear. Preferably the initialvolume of the loose material F is so much less than the cubic content ofthe tubular blank T, less the volume of the end of the punch 41 thatenters the blank as a pilot shown in Figures 18 and 19, that the fillermaterial P will not be confined in the blank nor have any substantialcompressive contact with the wrinkling wall of the blank or the end ofthe punch 41 prior to the extrusion of the leading leg of the blankaround the corner of the elbow as shown in Figure 19. The polyethyleneglycol that I prefer to use in the practice of my invention has amelting point of about 55 C., a molecular weight of about 6000 and isknown in the trade as Carbowax 6000: This material is obtainable ingranular or flake form, may be compacted or compressed to hardsubstantially solid form while remaining plastic under pressure. Thismaterial is of wax-like consistency and is soluble in water whereby tobe readily removed from the finished work. Moreover carbowax does notamalgamate, alloy or have a chemical reaction with the metal of thework.

In this modified form of my method l follow the major precepts andgeneral steps heretofore described with the modifications suggestedabove. The blank T having been partially filled with the filler F asshown in Fig. 18 is inserted or placed in the entering section 1 of thechannel C or the forming dies, and thereafter the ram Q engaging thetrailing end of the blank advances the blank T longitudinally throughthe bend of the channel to the position shown in Figure 19. Since thefiller F is in a loose condition within the blank T during the movementof the ram Q the leading leg of the blank is free to wrinkle and bedeformed by the working of the metal as it passes through the bendwhereby to assume a somewhat wrinkled condition more or less like theblanks B and 3 previously discussed. At the completion of the rammingstroke, as shown in Figure 19, it

11 will be observed that the filler F appears to more nearly fill theblank than it did when the blank was in its straight cylindrical form asshown in Figure 18. This follows the changed relationship of the surfacearea to the volume of the blank as the blank is given its elbowed formand as the leading leg thereof is permitted to wrinkle.

Prior to the forming stroke of the ram Q or at the end of the rammingstroke above described, the ram V is positioned in the forming leg 3 ofthe channel C so that the ram or abutment V presents a barrier tomovement of the leading end of the blank T. That is, the end face 44 ofthe ram Vpresents a substantially continuous face or abutment juxtaposedto the leading end of the blank T as shown in Figure 19. Preferably theram V need not necessarily contact the leading end of the blank T duringthe forming stroke, but the ram V is preferably so positioned that atthe end of the step yet to be described the ram V will simply be heldimmovable to bring about the desired form and shape of the leading legof the elbow.

With the parts in the position .shown in Figure 19, the plunger 41 ofthe ram Q is next advanced whereby to move inwardly of the trailing endof the blank T and engage the filler F. As the plunger 41 of the ram Qadvances it compresses the filler, see Fig. 20, whereby to force thefiller downwardly and leftwardly as viewed in the drawings therebyexerting an expanding pressure within the blank and the leading leg ofthe elbow. The pressure of the plunger 41 of the ram Q being transmittedto the inside surfaces of the elbowed blank forces out the wrinkles andother deformations that have inured to the walls of the blank during thefirst forming step and restores the leading leg to a right cylindricalform as shown in Figure 20 causing the extreme leading end wall 46 ofthe elbowed blank to take an almost true rectangular form at the endthereof bearing on the ram V as shown in Figure 20. Thereafter both therams Q and V with the plungers 41 may be withdrawn or backed up enoughto permit the ejection of the blank in its plain elbowed form from thedies. At this point the leading and trailing legs of the elbow will beof straight right cylindrical construction with the short radius bendtrue and full and having the shape desired. It then remains merely toremove the filler F and punch out end 46 and perform such additionalfinishing operations upon the elbow prior to or following the removal ofthe filler as may be advantageous to complete the manufacture ofthe'final commercial article.

A desirable modification of this form of my method may be carried outwith liquid filler introduced through the ram Q, the latter there takingmore the solid form of the ram V butprovided with an internal fluidpassage, not shown, leading to the interior of the blank T. With such aram appropriate external fluid connections and sources of controlledfluid pressures are provided and L the blank T may be advanced from theposition of Fig. 18 to that of Fig. 19 either devoid of fluid or fillercontent or with fluid therein at any desired .pressure. In the formerinstance the piece T will take -,substantially the form shown in Fig.1.9 whereupon the admission of fluid under pressure will dosubstantially the same work as compressing the loose filler describedabove with the results shown in Fig. 20. Fluid under controlled andpreferably moderate pressures may however be maintained inthe piece Tduring all or part of the forming stroke whereby to controllably resistthe tendency of the leading parts of the piece to wrinkle or deform asmay be desired as in the case,.f0r example, of thin walled tubing whichotherwise might tend to fracture if permitted to have complete freedomfor deformation. By the judicious and/or automatic regulation of theinternal fluid pressure in the piece T during selected parts of theforming stroke, .such as increasing the pressure progressively frombeginning to the end of the stroke an initial wrinkling maybe freelypermitted and then an increasing fluid pressure may be used tosubstantially merge the ironing effect of the final high pressure withthe last increments of the longitudinal motion of the forming stroke. Inthis way the actions between Figures 19 and 20 may take placesubstantially simultaneously.

While I have illustrated and described preferred and modified forms ofmy invention as now best known to me, changes, modifications andimprovements will occur to those skilled in the art upon theirunderstanding thereof without departing from my basic teachings or thespirit and substance of my invention, and I do not wish to be limited tothe preferred or specific forms herein disclosed or in. any manner otherthan by the claim appended hereto.

I claim:

Mechanism for working a straight tubular blank by longitudinal motionthrough the channel of a forming die to the 'form of a right angledelbow having the radius of curvature of its external surface at itsinside corner that is not substantially greater than one third theoutside diameter of the blank comprising a split forming die having anunobstructed right angled channel of uniform internaldiameter-corresponding to the outside diameter of the blank and havingan abrupt right angled bend smoothly joining entering and leavingpassages of the channel .with a radius of curvature corresponding to thesaid radius of curvature of the wrought elbow, said blank containing aquantity of freely flowable incompressible filler of greater volume thanthe wrought leg and bend of the elbow, a ram having an internal bore andslidably movable in the entering passage of the channel andengaging thetrailing end of the blank to forcibly move the blank and move theleading end of the blank through the bend in the channel and into theleaving passage thereof, a plunger slidably movable in the bore of said.ram and engageable with said filler independently of said ram, a secondram slidably movable in the said leaving passage of the channel, meansfor forcibly moving said first rarn, means restraining said plunger fromcompressingsaid filler until the leading end of the blank issubstantially fullymoved into the leaving passage of the die and forforciblymoving said plunger into forcible engagement with said fillerthereafter, and means for forcibly urging said second ram in saidleaving passage in opposition to the pressure created in said filler bysaid plunger.

References Cited in the file of this patent UNITED STATES PATENTS169,392 Wick-s Nov. 2, 1875 915,717 Andres Mar. 8, 1910 1,429,924Brinkman Sept. 26, 1922 1,598,893 Taylor Sept. 7, 1926 1,781,567 BohlingNov. 11, 1930 1,947,611 Moitke Feb. 20, 1934 2,138,199 Wendel Nov. 29,1938 2,335,342 Kvarnstrom Nov. 30, 1943 FOREIGN PATENTS 455,559 GermanyFeb. 3, 1928 412,075 Great Britain June 21, 1934

